Especially anthropomorphic monotheism. The idea of a God who acts like a pissed off, often stupid, individual, intervening in human affairs is pretty preposterous. Now if it was polytheistic, with a multiplicity of gods, that would be different. But Mr. Omnipotent, Omnipresent, Omniscient who also sits on a throne and judges people, who makes covenants and such, is a seriously deficient concept. At least in Islam God is much more of a non-anthropomorphized force.
Robert Anton Wilson once had a routine where he tried to find out how big God's cock was. He used different passages from the Bible that talk about god walking on earth, estimated his height, and then went through a process of deduction; Given that God would be well endowed, and he would be something like five hundred feet tall, how big would that make his cock, both flaccid and erect? What would the girth of God's cock be? Does it hang to the left or to the right? Veiny? Kinked?
Let's all give honor to the cock of God on this holy Easter Sunday.
*on edit: it's actually easy to tentatively determine how long God's cock would be. Let's take an easy ratio as our starting point: someone six feet tall who has a six inch cock. If you divide six feet by six inches you get twelve, since every foot is made up of twelve inches. This means that a six inch cock on a six foot man would be 1/12 of his height. Taking Robert Anton Wilson's 500 feet for God's height, the same proportion would be forty one feet, because 500/12 is forty one. But God is hung in our example. Really hung. So, let's just double that figure to make God have the equivalent of a twelve inch cock. That would mean that God's cock would be 82 feet long at full extension.
*on edit 2: "Phallus Dei" is also the name of a seminal album by Krautrock band Amon Düül II.